Barjot C, Rouanet P, Vigneron P, Janmot C, d'Albis A, Bacou F
Laboratoire de Différenciation cellulaire et Croissance, INRA, Montpellier, France.
J Muscle Res Cell Motil. 1998 Jan;19(1):25-32. doi: 10.1023/a:1005396125746.
We previously showed that satellite cells isolated from rabbit fast-twitch and slow-twitch muscles presented different behaviours in culture; cells from slow muscle differentiated more quickly and fused into more numerous myotubes than those from fast muscle. Moreover, only slow-muscle derived satellite cells expressed in vitro the slow type I myosin heavy chain isoform (MyHC). We wanted to investigate whether the properties of satellite cells originating from different muscles were under the influence of the adult fibre type on which they were located. For this purpose, we transformed the properties of the adult rabbit fast-twitch semimembranosus accessorius (SMa; approximately 100% type II fibres) and the slow-twitch semimembranosus proprius (SMp; 100% type I fibre) muscles by (1) cross-reinnervating the SMp with the main branch of the fast SMa nerve; or (2) electrical stimulation at 10 Hz of the SMa muscle. We studied their satellite cells in vitro. Five-month cross-reinnervation of the SMp induced a large shift of its MyHC type characteristics towards those of a fast muscle, and three-month electrical stimulation at low frequency transformed the fast-twitch SMa into a slow-twitch muscle, as shown by SDS-PAGE of MyHC. In spite of the transformation of their muscle characteristics, satellite cells in culture kept their original properties. Indeed, as shown by MyoD and myogenin gene expression as markers of fusion, satellite cells isolated from cross-reinnervated and from control SMp began to fuse by eight days of culture, and expressed MyoD and myogenin at that stage. Later they differentiated into numerous myotubes. Satellite cells isolated from electrically stimulated and control SMa presented a similar behaviour in culture: they did not express MyoD and myogenin at eight days, and fused by ten days into only a few myotubes. Moreover, MyHC gene expression showed that, in contrast with slow-muscle derived satellite cells, the type I MyHC gene was not expressed by satellite cells isolated from the stimulated SMa in spite of its homogeneous type I fibre composition. Taken together, these data support the idea that once constituted, muscle fibre types per se do not influence the properties of their associated satellite cells.
我们之前发现，从兔快肌和慢肌中分离出的卫星细胞在培养中有不同表现；慢肌来源的细胞比快肌来源的细胞分化更快，融合形成的肌管更多。此外，只有慢肌来源的卫星细胞在体外表达慢肌I型肌球蛋白重链异构体（MyHC）。我们想研究源自不同肌肉的卫星细胞的特性是否受其所在成体肌纤维类型的影响。为此，我们通过以下方法改变成年兔快肌半膜肌副肌（SMa；约100%为II型纤维）和慢肌半膜肌主肌（SMp；100%为I型纤维）的特性：（1）用快肌SMa神经的主支对SMp进行交叉神经支配；或（2）以10 Hz的频率对SMa肌肉进行电刺激。我们在体外研究了它们的卫星细胞。对SMp进行五个月的交叉神经支配使其MyHC类型特征大幅向快肌转变，低频电刺激三个月则将快肌SMa转变为慢肌，这通过MyHC的SDS - PAGE得以证明。尽管其肌肉特性发生了转变，但培养中的卫星细胞仍保持其原有特性。实际上，正如以MyoD和肌细胞生成素基因表达作为融合标志物所显示的那样，从交叉神经支配的和对照的SMp中分离出的卫星细胞在培养八天时开始融合，并在该阶段表达MyoD和肌细胞生成素。之后它们分化形成大量肌管。从电刺激的和对照的SMa中分离出的卫星细胞在培养中有类似表现：它们在八天时不表达MyoD和肌细胞生成素，十天时融合形成少量肌管。此外，MyHC基因表达表明，与慢肌来源的卫星细胞不同，尽管受刺激的SMa具有均匀的I型纤维组成，但其分离出的卫星细胞不表达I型MyHC基因。综上所述，这些数据支持这样一种观点，即一旦形成，肌纤维类型本身并不影响其相关卫星细胞的特性。
